1. Field of Invention
The present invention relates to an automobile headlight and parking light alarm system. More specifically, the present invention is connected to the parking or the headlight circuit and provides an audible alarm to alert the driver that the lights are energized while the engine is not operating.
2. Description of Prior Art
In the past a plurality of alarm devices have been developed to alert the driver that the lighting circuit is energized and the ignition circuit has been turned off. Examples of these devices are U.S. Pat. No. 4,194,175 by Eklund (1980) and U.S. Pat. No. 4,862,140 by Case (1989). To determine that the engine is not running several prior art devices monitor the ignition and lighting circuits as in U.S. Pat. No. 4,194,175 by Eklund (1980). A major disadvantage of these devices has been in their installation whereby the wires in the ignition and lighting circuits need to be correctly identified. Secondly, U.S. Pat. No. 4,862,140 by Case (1989) does not make use of the ignition circuit but monitors voltage levels at the headlight connector wiring to determine if the engine is running or not. This prior art invention uses three or four wires in its alarm to monitor the headlight signals at the connector. The installer must correctly identify the proper voltage polarity to install the device. The device also has the disadvantage of requiring calibration in either a factory environment or by the vehicle owner as wiring voltage drops are more likely to vary with different motor vehicles.
Problems such as identifying correct voltage polarity, calibrating the device and having to hookup to more than one vehicle electrical circuit are solved by the present invention. The first problem of identifying voltage polarity is solved by use of a diode bridge circuit. The need for calibration can be solved by monitoring the alternator ripple voltage. Also, only the circuit to which the alarm is connected is monitored.